Recording of data on a holographic storage device is performed by recording the intensity and direction of signal light reflected from a target object. The signal light from the target object interferes with reference light to produce an interference fringe corresponding to the intensity and direction of the signal light and the produced interference fringe is then recorded in a holographic storage medium including a material that reacts to the light according to the intensity of the interference fringe. Data recorded in the storage medium can be read using the reference light used in the process for recording the data and cannot be read using reference light with a wavelength and phase different from those of the reference light used for recording since the reference light with a different wavelength and phase passes through the data recorded in the recording medium.
Utilizing these holographic characteristics, a large amount of data can be recorded at the same place in a recording medium using different reference light beams, thereby enabling storage of a large amount of data in a small recording medium.
Generally, input data is modulated in order to record the data in a recording medium while minimizing the influence of ambient noise and to accurately reproduce the recorded data. Thus, the holographic storage device also uses a modulation code in order to correctly record and reproduce data.
In the holographic storage device, the modulation code needs to be designed so as to prevent the occurrence of Inter-Page Interference (IPI) which is interference between adjacent data pages and Inter-Symbol Interference (ISI) which is interference between pixels in a page when a data page is recorded in a medium.